There's a couple ways you could go with this, first you need to answer what slot you need them to fill....
1. WWP delivery system
2. Anvil Unit
3. Lot's of shooting
There's obviously much more to it, but you want them to fill a gap in what you have.
1. If you are using them for their webway portals then there are a couple things you can do.
I suggest using the Coven detachment as your way of WWP. You can get up to 6 haemonculus with WWP for 105pts each!!! With a min troop tax of 100pts, 2 min wrack squads. The nice thing about doing it this way is that the Haemon will convey fearless on turn 1, fear on turn 2. They all also give a -1 LD to anything within 6",(wracks included).
Or you can use the DE CAD and get a Archon with WWP for 10 points cheaper and a min troop tax would be 80. (Fear and Fearless is worth it!)
I suggest putting the troops in venoms with dual cannons, can't really go wrong there.
2. If you want a nasty melee unit then the coven detachment is still more than likely your best bet. Between Grotesquerie, Dark Artisan, and Corpsethief Claw you have some excellent potential for nasty melee units. Although the Corpsethief Claw runs 600pts at a bare minimum it is hard to find something like it anywhere else in the game. The Grotesquerie is my next favorite. The Dark artisan is nice but I have found it to be somewhat lack luster, it just doesn't do what I want an expensive unit to do.
3. If you are looking for just pure number of shots nothing can really beat a venom with 5 warriors and dual cannons for 105 points, other than your bikes. I would assume that as a Eldar player you probably don't need DE for shooting. The Razorwing fighters are nasty especially when you get 3 of them coming in on turn 2 dropping 12 s6 ap5 templates. At a min of 130 with dissies they can dish out damage, I don't suggest upgrading the splinter cannon TBH I just run mine with dark lances. Although if you keep the dissies on them and upgrade the cannon they will threaten FMCs.
4. You can build a null deployment army around the Coven formation Scalpel Squadron since it comes in turn 1.
5. You can run a nasty flyer list with the Realspace Raiders Detachment, the Flyer formation from your dex. Which would be 9 flyers on the table with a top end potential of 15 flyers from 3 sources, RRD(9), Formation(3), Eldar Cad(3?). Although most people would argue against running 3 Voidraven Bombers(I would).
So what you need to do is find what gap you are looking to fill and then we can break it down from there. Not really sure what you are looking for.